Injection-compression molding machine and method of molding by using the machine

ABSTRACT

A method of molding a plastic resin having for its object to enable the filling or spreading speed of a molten resin in a mold to be controlled in compliance with the shape of an article to be molded by changing the opening and closing speed of the mold or the injecting speed of the molten resin in an injection unit in compliance with the amount of the molten resin charged into the mold or the amount of the molten resin injected by the injection unit so that a stable molded article can be produced in a short time even in case the shape of a product to be molded is changed, and an injection-compression molding machine constructed to achieve the molding method. This injection-compression molding machine has a compression unit (21) for clamping the mold, an injection unit (10) for injecting the molten resin into the mold, a detector (25a) for detecting the stroke of the compression unit, a detector (26a) for detecting the opening and closing speed of the mold, input component (25b, 26b, 16b) for setting inputs of the stroke of the compression unit, the opening and closing speed of the mold, and the injecting speed, respectively, a controller (40) including an interface (45), a compression unit driving component (21c), and an injection unit driving component (14c).

TECHNICAL FIELD OF THE INVENTION

This invention relates to an injection-compression molding machine formolding a plastic resin and a method of molding by using the moldingmachine.

BACKGROUND TECHNIQUE OF THE INVENTION

The conventional method of molding by using a compression moldingmachine as disclosed, for example, in the specifications and drawings ofJapanese Laid-open Specification Nos. SHO 60-21225 and SHO 60-110419 ofJapanese Patent Applications, respectively, is conducted by charging aplastic resin material to be molded into a heated mold, actuating themolding machine thereby pressuring the material at a low pressure tofill the mold with the resultant molten resin, and then opening theupper and lower molds once slightly to vent the gaseous matter presentin the material, pressurizing the material again at a high pressure,continuing the pressurizing and the heating until the material has beencured, and then opening the mold and taking out the molded article.Whilst, in the method of injection and compression molding, when amolten resin material is injected into a mold, the injection flow rateand the injecting speed of the molten resin are controlled by the movingspeed and the pressing force of a screw.

In the above-mentioned conventional compression molding method, however,since the resin to be molded is subjected in turn to a low pressure anda high pressure, the number of the processes is increased, and alsosince after the mold is filled with the resin it is subjected to apredetermined pressure, there is a tendency of molded articlesundergoing shrink marks or warping.

Further, in the method of molding by using the injection-compressionmolding machine, a molten resin is injected into a mold in such a mannerthat the moving speed and the pressure of the screw is varied with theshape of the mold used and that of an article to be molded. In thiscase, since the flow speed of the molten resin will change in compliancewith the shape of the mold and that of an article to be molded, the moldcan not be filled uniformly with the molten resin with the result thatthe molded articles tend to have defects such as haze weld lines, flowmarks and entrap gases.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentionedcircumstances, and has for its object to provide aninjection-compression molding machine and a method of molding by usingthe molding machine wherein the injecting speed and the injectionflow-rate of a molten resin by the injection unit can be varied incompliance with the filling speed (or spreading speed) of themolten-resin within the mold and/or the injecting speed of the moltenresin can be varied in compliance with the filling speed so that, whenthe molten resin injected by the injection unit into the mold may fillthe latter so as to spread therein as it is compressed in the mold by amold compression unit, the mold can be filled uniformly with the moltenresin.

To achieve the above-mentioned object, according to a first aspect ofthe present invention, there is provided an injection-compressionmolding machine having a compression unit for clamping a mold and aninjection unit for injecting a molten resin into the mold, the moldingmachine comprising a means for detecting the stroke of the compressionunit; a means for detecting the injecting speed of the injection unit;an input means for setting the stroke of the compression unit; an inputmeans for setting the injecting speed of the injection unit; a strokesignal generator means for converting the detected stroke of thecompression unit into a stroke signal corresponding to a value presentby the stroke setting input means; a means for generating an injectingspeed signal for the injection unit in response to the stroke signal;and an injection unit driving means adapted to be actuated in responseto the injecting speed signal.

To achieve the above-mentioned object, according to a second aspect ofthe present invention, there is provided an injection-compressionmolding machine having a compression unit for clamping a mold and aninjection unit for injecting a molten resin into the mold, the moldingmachine comprising: a means for detecting the stroke of the compressionunit; a means for detecting the opening and closing speed of the mold;an input means for setting stroke of the compression unit; an inputmeans for setting the opening and closing speed of the mold; a strokesignal generator means for converting the detected stroke of thecompression unit into a stroke signal corresponding to a value preset bythe stroke setting input means; a means for generating an opening andclosing speed signal for the mold in response to the stroke signal, anda compression unit driving means adapted to be actuated in response tothe mold opening and closing speed signal.

To achieve the above-mentioned object, according to a third aspect ofthe present invention, there is provided an injection-compressionmolding machine having a compression unit for clamping a mold and aninjection unit for injecting a molten resin into the mold, the moldingmachine comprising: a means for detecting the injecting speed of theinjection unit; a means for detecting the opening and closing speed ofthe mold; an input means for setting the injecting speed of theinjection unit; an input means for setting the opening and closing speedof the mold; an injecting speed signal generator means for convertingthe detected injecting speed of the injection unit into an injectingspeed signal corresponding to a value preset by the injecting speedsetting input means; a means for generating an opening and closing speedsignal for the mold in response to the injecting speed signal; and acompression unit driving means adapted to be actuated in response to themold opening and closing speed signal.

To achieve the above-mentioned object, according to a fourth aspect ofthe present invention, there is provided a method of molding a plasticresin by using the injection-compression molding machine according tothe first aspect, comprising the steps of detecting the amount of themolten resin injected into the mold in the compression unit, andchanging the injecting speed of the molten resin to be injected by theinjection unit into the mold in compliance with the detected amount ofthe molten resin.

To achieve the above-mentioned object, according to a fifth aspect ofthe present invention, there is provided a method of molding a plasticresin by using the injection-compression molding machine according tothe second aspect, comprising the steps of detecting the amount of themolten resin injected into the mold in the compression unit, andchanging the opening and closing speed of the mold in compliance withthe detected, amount of the molten resin.

To achieve the above-mentioned object, according to a sixth aspect ofthe present invention, there is provided a method of molding a plasticresin by using the injection-compression molding machine according tothe third aspect, comprising the steps of detecting the injecting speedof the molten resin by the injection unit, and changing the opening andclosing speed of the mold in compliance with the detected injectingspeed.

According to the above-mentioned injection compression molding machinehaving the above-mentioned aspects incorporated and the method ofmolding by using the molding machine, since the filling speed (orspreading speed) of the molten resin in the mold is controlled by theinjecting speed (or the injection flow rate) of the molten resin and/orthe opening and closing speed of the mold which are determined by thestroke of the compression unit matching the shape of an article to bemolded, a molded article of a stable quality which is free from surfacedefects has little residual stress and which has limited deviation inthickness and can be obtained in a short time with excellent transfer ofconfigurations on the metallic surface of the mold to the moldedarticle.

The above-mentioned and other objects, aspects and advantages of thepresent invention will be apparent to those skilled in the art by makingreference to the following description and the accompanying drawings inwhich preferred embodiments incorporating the principles of the presentinvention are shown by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view showing the overall arrangement of aninjection-compression molding machine according to the presentinvention;

FIG. 2 is an explanatory view including in combination a schematiclongitudinal sectional view showing the arrangement of principal partsof the injection-compression molding machine according to the presentinvention, and a block diagram thereof.

FIG. 3 is a block diagram showing a controlling system for theinjection-compression molding machine according to the presentinvention;

FIG. 4 is a flow chart showing a first embodiment of the method ofmolding according to the present invention.

FIG. 5 is an explanatory regarding the operation of the embodiment asshown in FIG. 4;

FIG. 6 is a flow chart showing a second embodiment of the method ofmolding according to the present invention, and

FIGS. 7, 8 and 9 are flow chart showing third, fourth and fifthembodiments of the method of molding according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described below with reference to theaccompanying drawings in which preferred embodiments of the presentinvention are shown.

FIG. 1 is an overall constructional view showing one embodiment of theinjection-compression molding machine according to the presentinvention. In FIG. 1, reference numeral 1 denotes aninjection-compression molding machine, 10 an injection unit, 20 a pressprovided with a compression unit 21, and 30 a mold.

The injection unit 10 is slidably mounted on a bed 2 of theinjection-compression molding machine 1 through a slider 12 fixedlysecured to an injection cylinder 11. The mold is made up of an uppermold 31 and a lower mold 32. The upper mold 31 is fixedly secured to aslide 22 of the compression unit 21 of the press 20, whilst the lowermold 32 is fixedly secured to a bed 27. A plastic resin within the mold30 is pressurized by the depressing force developed by the slide 22, andalso the opening and closing speed of the mold 30 is associated with thespeed of the slide 22.

In FIG. 2, a screw 13 is mounted closely within the injection cylinder11 of the injection unit 10. Further, this screw 13 is connected to apair of pistons 14a within corresponding cylinders 14 through a bracket15 so that it may be slidably moved in the directions shown by referencecharacter Z when the pistons 14a within the cylinder 14 are driventhereby injecting the molten resin.

The speed of sliding movement of the screw 13 which is proportionate tothe injecting speed of the molten resin by the injection unit 10 iscontrolled by the discharge rate of pressurized fluid which iscontrolled by a flow rate controlling means 28 or a variabledisplacement pump, not shown, and is measured by means of a speed sensor16. Further, the position of the screw 13 is measured by means of aposition sensor such as, for example, a potentiometer 17 or the like sothat measurement of the injection speed (or amount of injection) of themolten resin can be made.

A plastic resin is thrown through or supplied from a hopper 18 into theinjection cylinder 11, and is fused by the action of a heater 18a. Themolten resin is pressurized by the screw 13 so that it may be injectedthrough a flow passage 19 into the lower mold 32. The mold 30 has a flowpassage 33 formed in the lower mold 32 and which leads to a productmolding portion 34. One side of the product molding portion 34 is formedby the lower mold 32, and the other side thereof is formed by the uppermold 31 located opposite to the lower mold 32. The arrangement is madesuch that the inner space or volume of the product molding portion 34may be expanded and contracted by the vertical movement of the uppermold 31. The relative opening and closing speed of the upper and lowermolds and the pressure of the molten resin introduced into the productmolding portion 34 are determined by the moving speed and the depressingforce of the upper mold 31. The moving speed and the depressing force ofthe upper mold 31 are controlled by the moving speed and the extrudingforce of a piston 23a mounted in a hydraulic cylinder 23 for driving thecompression unit 21 of the press 20 having the upper mold 31 mountedthereon. The moving speed and the extruding force of the piston 23adepend in turn on the controlled flow rate and the pressure of the fluidunder pressure in a hydraulic circuit having a flow rate controllingmeans 29 incorporated therein.

The slide 22 of the compression unit 21 is fitted with a potentiometer25 and a speed sensor 26, which detect the stroke position and themoving speed of the slide 22, respectively.

In FIG. 3, a controller 40 comprises a CPU 41, a RAM 42, a ROM 43 and aclock oscillator 44. The controller 40 is further provided through aninterface 45 with a means 16a for detecting the injecting speed of theinjection unit 10 which consists of the speed sensor 16, etc. formeasuring the moving speed of the screw 13 mounted within the cylinder11, a means 26a for detecting the opening and closing speed of the moldwhich consists of the speed sensor 26, etc. for measuring the openingand closing speed of the mold 30, and a means 25a for detecting thestroke of the compression unit which consists of the potentiometer 25,etc. for measuring the stroke position of the mold 30. The controller 40is yet further provided through the interface 45 with an input means 16bfor setting the injecting speed (or amount of injection) of theinjection unit 10 for setting the moving speed of the screw 13 mountedwithin the injection cylinder, an input means 26b for setting theopening and closing speed of the mold 30, and in input means 25b forsetting the stroke of the compression unit for setting the strokeposition of the mold 30. Further, the controller 40 is arranged suchthat is may generate a signal to control a driving means 21c for thecompression unit 21 which consists of the hydraulic cylinder 23, etc.for controlling the opening and closing speed of the mold, and a drivingmeans 14c for the injection unit which consists of the cylinder 14, etc.for controlling the moving speed of the screw 13 mounted in theinjection cylinder; that is; the injection speed (amount of injection)of the molten resin, respectively, in response to each of the signalsdetected relative to each of the values preset bu the input settingmeans; in other words; in response to each of the signals to beoutputted when each of the detected values corresponds to the value setby each input setting means.

The first embodiment of the method of molding by using theinjection-compression molding machine having the above-mentionedconstruction will first be described below with reference to FIGS. 4 and5.

The injection-compression molding machine 1 is started when the mold 30is opened. With the start of the injection-compression molding machine1, a command on the opening and closing speed of the mold (STEP 51), anda command of the stroke position of the mold (STEP 52) are given, and atSTEPS 53 and 54 comparison between the current mold opening and closingspeed and a commanded value, and comparison between the current strokeposition of the mold and a command value, respectively, are made. Whenthe current opening and closing speed and the current stroke of the moldbecome as commanded, a command on the speed of the screw 13 mountedwithin the injection cylinder (STEP 55) for determining the injectionspeed (Va) of molten resin matching the shape of a product to be molded(at position 1a in FIG. 5), a command on the opening and closing speedof the mold for the shape of a product to be molded next (STEP 56), anda command on the stroke position (lb) of the mold for continuing thatcommand on the speed (STEP 57) are given.

STEPS 58, 59 and 60 are repeated until the moving speed of the screwmounted within the injection cylinder, the opening and closing speed andthe stroke position of the mold become as commanded. When the threevalues have become as commanded, the system is returned to STEP 55 wherecommands on the next injection speed (Vb), the next mold opening andclosing speed, and the next stroke position (lc) of the mold, all ofwhich are matching the shape of a product to be molded next, are given.

The stroke position of the mold matching the shape of a product to bemolded in inputted by the injection speed (amount of injection) settinginput means, and the injecting speed of the molten resin inputted by theinput means at the stroke position of the mold is changed, and theninjection of the molten resin is made.

In the next place, the second embodiment of the method of molding willbe described with reference to FIG. 6. The injection-compression moldingmachine 1 is started, and a command on injection of the molten resininto the mold is given. (STEP 71).

At STEP 72, the amount of injection of the molten resin is measured bymeans of a position sensor for the injection cylinder such as thepotentiometer 17, etc. attached to the injection cylinder 11. When aspecified amount of the molten resin has been injected (STEP 72), thecontroller 40 will give a command on the moving speed of the screwmounted within the injection cylinder (STEP 73), a command on theopening and closing speed of the mold (STEP 74), and a command on thestroke position of the mold (STEP 75) in the same manner as in the caseof the first embodiment, and then conduct the same control as that ofthe first embodiment. Further, in this case, the amount of injection ofthe molten resin by the injection unit may be determined by the movingspeed of the screw and the timing for opening and closing of the moldpreset by the clock oscillator.

In the above-mentioned first embodiment, the sequence among STEPS 55 to57 and STEPS 58 and 59 may be changed.

Further, while in the above-mentioned embodiments a hydraulicallyactuated type press comprising a hydraulic cylinder is used as the pressfor the compression unit of the mold, a mechanical press of a cranktype, or of a crankless type may be used instead. Further, while a screwis used in the injection-compression molding machine, it is needless tosay that a plunger may be used alternatively.

While there is described hereinabove the example wherein the injectionspeed of the molten resin is varied in multiple stages in response tothe stroke position of the molding unit, the arrangement may be madesuch that the injection speed can be varied continuously.

Subsequently, the third embodiment of the method of molding will bedescribed with reference to FIG. 7.

The injection-compression molding machine 1 is started, and a command oninjection of the molten resin into the mold 30 is given. (STEP 81)

At STEP 82, whether or not a specified amount of the molten resin hasbeen injected into the mold 30 is judged by means of the means 25a fordetecting the stroke of the mold 30. In case it is confirmed that aspecified amount of resin has been rejected, the controller 40 will givea command on the mold opening and closing speed for pressurizing themolten resin and injecting it into the mold (STEP 83), and a command onthe stroke position of the mold for changing the opening and closingspeed of the mold at a position matching the shape of a product to bemolded. (STEP 84). Whilst, in case a specified amount of the moltenresin has not yet been injected, the above-mentioned operation isrepeated until the mold is filled with a specified amount of the moltenresin. Subsequently, STEPS 85 and 86 are repeated until the opening andclosing speed and the stroke position of the mold become as commanded.When the opening and closing speed and the stroke position of the moldhas reached their respective command values, the system will return toSTEP 83 where a command on the next opening and closing speed of themold inputted by the mold opening and closing speed input means 26bmatching the shape of a product to be molded next is given.

Such STEPS are conducted in multiple stages in compliance with the shapeof a product to be molded.

Next, the fourth embodiment of the method of molding will be describedwith reference to FIG. 8. The injection-compression molding machine 1 isstarted, and a command on injection of the molten resin into the mold 30is given. (STEP 91)

At STEP 92, whether or not a specified amount of the molten resin hasbeen injected into the mold is judged by means of the means 16a fordetecting the injection speed of the resin by the injection cylindersuch as the speed sensor 16, etc. fitted to the injection cylinder 11.When it is confirmed that a specified amount of resin has been injectedinto the mold, the controller 40 will give the compression unit drivingmeans 21c a command on the opening and closing speed of the mold forpressurizing the molten resin so as to fill the mold with it (STEP 93),and also give the injection unit driving means 14c a command from thepotentiometer 17 on the stroke position of the screw within theinjection cylinder for changing the amount of the molten resin to beinjected by the injection unit at a position of the screw matching theshape of a product to be molded. Whilst, in case a specified amount ofthe resin has not yet been injected, the above-mentioned operation isrepeated until the mold is filled with the plastic resin. After that,STEPS 95 and 96 are repeated until the opening and closing speed of themold and the amount of the molten resin injected by the injectioncylinder become as commanded. When the opening and closing speed of themold and the amount of the molten resin injected into the mold havereached their respective commanded values, the system will return toSTEP 93 where a command on the next opening and closing speed of themold matching the shape of a product to be molded next.

Next, the fifth embodiment of the method of molding will be describedwith reference to FIG. 9. The injection-compression molding machine 1 isstarted, and a command on injection of a molten resin into the mold 30is given. (STEP 101)

At STEP 102, whether or not a specified amount of the molten resin hasbeen injected into the mold is judged by means of the mold strokedetector means 25a such as the potentiometer 25 at the stroke positionof the mold. When it is confirmed that a specified amount of the resinhas been injected into the mold, at STEPS 103 and 104 the controller 40will give commands similar to those at STEPS 94 and 95 in the fourthembodiment. Whilst, in case a specified amount of the resin has not yetbeen injected, the injection is made repeatedly until the mold is filledwith a predetermined amount of resin.

At STEP 105, whether or not the opening and closing speed of the moldhas become as commanded is detected by means of the means 26a fordetecting the opening and closing speed of the mold, such as, the sensor26 or the like, and the current opening and closing speed of the mold iscompared with its commanded value by the controller 40. In case thecurrent mold opening and closing speed has reached a commanded value,the system will move to STEP 106 where the current amount of the moltenresin injected by the injection cylinder will be compared with itscommanded value.

In case it is confirmed at STEP 106 that a commanded amount of themolten resin is injected, the system will return to STEP 103 where acommand on the next opening and closing speed of the mold matching theshape of a product to be molded next.

In case it is confirmed at STEP 106 that a specified amount of the resinhas not yet been reached, the system will return to STEP 105 whereconfirmation of the mold opening and closing speed is made, and at STEP106 the amount of the resin injected by the injection cylinder iscompared with its commanded value. STEPS 105 and 106 are repeated untila commanded amount of the molten resin has been injected into the mold.

Thus, the fifth embodiment is a combination of the third and fourthembodiments. It is also possible, according to the sequence reverse tothat of the fifth embodiment, to detect previously the amount of themolten resin injected by the injection cylinder and then detect theamount of the resin charged into the mold thereby controlling theopening and closing speed of the mold. Whilst in the above-mentionedembodiments detection of the amount of the molten resin to be injectedby the injection cylinder into the mold is made by detecting the strokeposition of the molding or injection unit 21, it may be conductedaccording to the inflow speed and outflow speed of the resin and thetiming of the opening and closing of the mold preset by the clockoscillator 44, which can be incorporated in each of the flow charts toconduct the control.

Further, regarding the configuration of the flow charts, it is possibleto change return to which STEP in case the result is "NO", in FIGS. 8and 9, or change the control sequence of STEPS 103 and 104, or changethe control sequence so that STEPS 103 and 105 are previously performed,and then STEPS 104 and 106 are performed, as occasion demands.

We claim:
 1. A method of molding a plastic resin comprising the steps of:opening a mold of an injection-compression molding machine, said injection-compression molding machine including a compression unit for clamping the mold and an injection unit for injecting a molten rein into the mold; setting a command for an opening and closing speed of the mold and setting a command for a stroke position of the mold; comparing a current mold opening and closing speed with the commanded opening and closing speed of the mold and comparing a current stroke position of the mold with the commanded stroke position of the mold; setting a command matching a shape of a product to be molded for an injection speed of the molten resin when the current opening and closing speed and the current stroke of the mold become as commanded; and injecting said molten resin from said injection unit into said mold in compliance with a filling speed of the molten resin within the mold so that the molten resin spreads uniformly therein as it is compressed in the mold by said compression unit.
 2. The method of molding a plastic resin according to claim 1 further comprising the steps of:detecting the amount of the molten resin injected into said mold in said compression unit, and changing the injecting speed of the molten resin to be injected by said injection unit into said mold in compliance with the detected amount of the molten resin.
 3. A method of molding a plastic resin comprising the steps of:opening a mold of an injection-compression molding machine, said injection-compression molding machine including a compression unit for clamping the mold and an injection unit for injecting a molten resin into the mold; measuring the amount of the molten resin in said injection unit; setting a command for an injection speed of the molten resin into the mold; setting a command for an opening and closing speed of the mold and setting a command for a stroke position of the mold; comparing a current injection speed with the commanded injection speed, comparing a current mold opening and closing speed with the commanded opening and closing speed of the mold and comparing a current stroke position of the mold with the commanded stroke position of the mold; and injecting said molten resin from said injection unit into said mold in compliance with a filling speed of the molten resin within the mold when said current injection speed, said current mold opening and closing speed and said current stroke position are as commanded so that the molten resin spreads uniformly therein as it is compressed in the mold by said compression unit.
 4. A method of molding a plastic resin comprising the steps of:opening a mold of an injection-compression molding machine, said injection-compression molding machine including a compression unit for clamping said mold and an injection unit for injecting a molten resin into the mold; injecting molten resin into said mold; detecting the amount of molten resin in said mold; comparing the amount of molten resin in said mold with a specified amount of molten resin; setting a command for a mold opening and closing speed for pressurizing the molten resin if the specified amount of molten resin equals the detected amount of molten resin; and continuing to inject resin into the mold if the detected amount of molten resin is less than the specified amount of molten resin.
 5. An injection-compression molding machine comprising:a compression unit for opening and closing a mold; an injection unit for injecting a molten resin into at least one cavity formed in the mold; means for detecting a stroke of said compression unit; means for detecting an injecting speed of said injection unit; input means for setting the stroke of said compression unit; input means for setting the injecting speed of said injection unit; stroke signal generator means for converting said detected stroke of the compression unit into a stroke signal corresponding to a value preset by said stroke setting input means; means for generating an injecting speed signal for said injection unit in response to said stroke signal; injection unit driving means for driving said injection unit adapted to be actuated in response to the injecting speed signal; controller means for controlling the injecting speed of the molten resin and the stroke of said compression unit, so that when the molten resin is injected by said injection unit into said mold as a result of actuation of said injection unit driving means, the injecting speed of the molten resin can be varied in compliance with the filling speed of the molten resin within the mold so that the molten resin spreads uniformly therein as it is compressed in the mold by said compression unit.
 6. The injection-compression molding machine according to claim 5, further comprising means for detecting an opening and closing speed of said mold, input means for setting the opening and closing speed of said mold, and means for generating an opening and closing signal for said mold in response to the stroke signal.
 7. The injection-compression molding machine according to claim 6, further comprising compression unit driving means for driving said compression unit adapted to be actuated in response to the stroke signal.
 8. The injection-compression molding machine according to claim 5, wherein said injection unit includes an injection cylinder with a screw mounted therein, said screw being connected to a pair of pistons within corresponding cylinders through a bracket so that the screw may be slidably moved along a central axis of said injection cylinder so that the speed of said screw is proportionate to the injecting speed of the molten resin and is controlled by a discharge rate of pressurized fluid which is controlled by a flow rate controlling means, whereby molten resin in said injection cylinder is pressurized by the screw so that it may be injected through a flow passage into the mold.
 9. The injection-compression molding machine according to claim 5, wherein said compression unit includes a piston mounted in a hydraulic cylinder for driving the compression unit, whereby the stroke of the compression unit and the pressure of the molten resin introduced to the mold are determined by the moving speed and the depressing force of the upper mold, which are controlled by the moving speed and the extruding force of the piston. 